While working in your Python app, you may need to install packages to add extra functionality. Those packages may come in different versions.
To deal with package installation, Python has a tool that works like
gem in Ruby,
npm in node, etc. It's called
To deal with package versions, Python has another tool which is equivalent to
bundler in Ruby, the
package.json file in node, etc. It's called
To install pip:
$ curl https://bootstrap.pypa.io/get-pip.py $ sudo python get-pip.py
To install virtualenv:
$ sudo pip install virtualenv
The first step when working on a Python app is to create a local environment to install things. Be aware that some files will need execution permissions. In the directory of our future app, type:
$ virtualenv venv $ . venv/bin/activate (venv) $
This will create a directory
venv where everything our app needs will be installed. We also have to activate it, which gives us a special prompt (
(venv) $) to let us know that we are in a parallel universe where our packages "exist".
To install your app packages in its environment, for example, if you wanted to install the requests package:
(venv) $ pip install requests (venv) $ pip freeze # will print all installed packages and their versions. (venv) $ DO YOUR STUFF HERE
When we are finished working on our app we can deactivate the environment to recover our normal prompt (going back to our universe), or close that terminal window.
(venv) $ deactivate venv $
Say hi to virtualenvwrapper: virtualenv on steroids
There is a wrapper around
virtualenvwrapper, that offers more functionality. You can learn more about it in its official website.
To install: First check if you have it installed:
$ dpkg -l | grep virtualenvwrapper
Then install it:
$ sudo apt-get install virtualenvwrapper
To create an environment:
$ mkvirtualenv -a PATH_TO_YOUR_APP YOUR_APP_NAME
If you want to create it with a specific version of Python:
$ mkvirtualenv -a PATH_TO_YOUR_APP --python=/usr/bin/python3.4 YOUR_APP_NAME
This makes a dir for the project inside
/home/admin/.virtualenvs. Edit the
.project file inside the project's folder to point it to the path where the project lives.
After that, you have these commands available:
cdvirtualenv: takes you to the virtualenv directory in your home directory.
cdproject: will take you to the path where your project lives.
workon YOUR_APP_NAME: will take you to the path AND inside environment of your project.
This tool is so cool and convenient that it became the environment tool that I use for everything I do in Python these days.
Other handy tools when working with Python
Flake8 as a linter
E501 in "Ignore Error codes" in the package settings. You can also specify this on the terminal.
Pry-like shell with IPython
IPython is a tool that you can install together with Django as an alternative to the Django shell, and it gives you bash completion, colored output, etc. For example, something that you can do is
dir(classname), which is equivalent to
cd classname in pry, i.e., a command that allows you to see the guts of a class, its methods, member fields, etc.
Debugging with ipdb
This is the equivalent of throwing a
binding.pry in your code in Ruby. Instead of
binding.pry, in Python you can type:
import ipdb; ipdb.set_trace()
It looks long, but when I start typing
import ipdb in atom on a Python file, it autocompletes the whole command (it also does the same with
Some handy commands to move through the code that I haven't check if pry has as well are:
n: next line
up: go up in the stack trace
down: go down in the stack trace